Holocene paleoenvironmental reconstructions using subfossil chironomid
assemblages from the sediment of a glacial lake in the southern Bohemia:
preliminary results.
Jolana Tátosová1, Josef Veselý2, Evžen Stuchlík3
1
Institute for Environmental Studies, Faculty of Science, Charles University in Prague, Benátská 2,
128 01 Prague, Czech Republic,
2
Czech Geological Survey, Geologická 6, 152 00 Prague 5, Czech Republic
3
Hydrobiological Station, Institute for Environmental studies, Charles University in Prague, PO
Box 47, CZ-38801 Blatná, Czech Republic
Contact: Jolana Tátosová (jolana@blatna.cuni.cz)
A faunal record of chironomid remains was analyzed in upper 280 cm of a 543 cm
long sediment core from Plešné Lake, the Bohemian Forest, Czech Republic.
Plešné Lake (1,090 m a.s.l.) is one of the eight small glacial lakes situated in Central
Europe between Czech Republic, Germany, and Austria. The lake is located in the
southeast relatively remote and uninhabited part of the Bohemian Forest (48º47’N,
13º52’E) at climatically sensitive place. The lake is mesotrophic (TP on average 11 μg L1
) and dimictic with the area of 7.5 ha, maximum depth of 18 m, has theoretical water
residence time of 0.73 yr at present (Majer et al., 2003). The bedrock is built-in granite.
The forest covering most of the waterhed is on average 160 years old and dominated by
Picea excelsa. Recent (1961 to 2004) average of annual and July temperatures are 4.4
and 13.1 °C, respectively. The lake is on average 135 days/ yr covered by ice.
Plešné Lake was already atmospherically acidified in the early 1960s. Strong
acidification progressed until the mid-1980s when pH of water ranged between 4.4 and
4.7 (Kopáček et al., 1998). At present, the lake is in the process of chemical recovery
from acidification (Majer et al., 2003)
The chronology of whole sediment core was established by means of AMS-dated
plant macroremains in the Holocene and by matching rubidium concentrations with δ
curve in the Greenland ice core GISP2 in the Late-Glacial time. Errors of dating by
18
O
14
C-
and Rb-methods are ≤ 200 years (Veselý et al., 2006 submitted). The age of core bed
was ~14.6 ka BP. The uppermost 50-cm part of the sediment was less compressed. The
dating of this part of core was improved by using of characteristic peaks in lead (Pb)
th
th
concentration in the 14 and in the 16 century AD (Veselý, 2000), connected to the
extensive smelting in the Middle Ages and the Renaissance. The resolution of individual
3-cm sediment layers is ~115 years in the Holocene and between 35 and 70 years in the
Late-Glacial, depending on the sedimentation rate.
Chironomid head remains were analyzed from upper 280 cm of sediment core, which
represents 10.4 ka BP. Wetter climate after the 2nd Preboreal climate oscillation (≤ 10.5
ka BP) led to a strong domination of reophilic species Corynoneura scutellata gr. and,
due to the increase accumulation of allochtonous material, also Heterotrissocladius
marcidus. During the period 8 - 3 cal. ka BP, the cold adapted taxa dominated at the
beginning of this period. In the second part of this period, indermediate taxa were mainly
present, and new species associated with macrophytes (Cricotopus) appeared
irregularly. Important changes in profundal chironomid species structure took place
during the next period 3 ka BP- present. H. marcidus and H. grimshawi was replaced by
Procladius and the species of tribus Tanytarsinii. Also Chironomus sp. was present in
small abundances. Intermediate and warm adapted taxa dominated in this time. This
change shows a significant shift in the lake productivity. A marked oscillation is evident in
time of 700 – 170 BP (LIA), when the smallest total abundance was found and the cold
adapted taxa appeared again.
Majer, V., Cosby, B.J., Kopáček, J. & Veselý J. 2003. Modelling Reversibility of Central European
Mountain Lakes from Acidification: Part I - The Bohemian Forest. Hydrol. Earth System Sci. 7:
494-509.
Kopáček, J. Hejzlar J., Stuchlík, E., Fott, J. & Veselý J. 1998. Reversibility of acidification of
mountain lakes after reduction in nitrogen and suphur emissions in Central Europe. Limnol.
Oceanogr., 43: 357-361.
Veselý, J., Majer, V., Pokorný, P. & Kopáček, J. 2006. Dating of lake sediment by comparison of
18
rubidium concentration with δ O in Greenland ice. Quarter. Geochronol., submitted
Veselý, J. 2000. The history of metal recorded in the sediments of Bohemian Forest lakes: Since
the Bronze Age to the present. Silva Gabreta 4: 147-165.